Along with Pacino, director Francis Ford Coppola and stars Robert De Niro, James Caan, Robert Duvall, Diane Keaton and Talia Shire all took part in a panel to talk about the origins of the story.

The actor revealed he'd been under a lot of pressure with Paramount who didn't want him cast, making him do "countless" screen tests and ultimately he wasn't sure the role of Mafia boss Michael Corleone was for him.

"It seemed like I was always testing," Pacino said. "I was still testing after I got the part."

He said that, ultimately, his filming experience ended up with him breaking down to his co-star Diane Keaton after filming one night, telling her: "We're gone. It's over. This is the worst film ever made."